Polybutene is generally obtained by polymerizing olefin components with carbon number 4 (C4) derived during cracking of naphtha using a Friedel-Craft type catalyst and has a number average molecular weight (Mn) of about 300 to about 5,000. Raw materials used include isobutene with high purity, C4 raffinate-1 and a butane-butene fraction (B-B fraction). In the case where the isobutene with high purity used after diluting in a solvent of butanes is used as the raw materials, the content of the halogens in the polybutene and LP (or an isobutene oligomer, hereinafter will be referred to as light polymers) thus prepared is not high. However in the case where among the C4 material the C4-raffinate-1 remaining after the extraction of 1,3-butadiene, and the butane-butene fraction which is a C4 mixture derived during purifying crude oil, etc., are used as the raw materials, the content of the halogens in the polybutene and the light polymers thus prepared is high. In the C4-raffinate-1 and the butane-butene fraction, paraffin of isobutene and normal butane, and olefin of 1-butene, 2-butene, 30 to 50 wt % of isobutene, etc. are included, and the halogen content therein is high under the influence of the 1-butene. Particularly, in the light polymers produced as a by-product during preparing polybutene by polymerizing the above materials, hundreds to thousands ppm of organic halogens from a Friedel-Craft catalyst are present. Due to the organic halogens, the direct use of the light polymers as a fuel additive, a friction modifier, a non-aromatic organic solvent or the additive of cosmetics is difficult, and the light polymers including a halogen component is discarded or sold as a fuel oil at low price.
Light polymers generated during polymerizing polybutene is generally composed of an auxiliary cocatalyst of ethers, a compound with carbon number 4, which does not participate in the polymerization, and a material of C8, C12, C16, C20, C24, C28 or more, and has a viscosity of 3 cSt at a temperature of 40° C. According to the catalyst used, organic halogens in which chlorine or fluorine is combined are included in a ratio of 100 to 2,000 ppm. When the organic halogens are added to a fuel, an engine may be corroded, and environmental contamination may be induced due to exhaust fumes. In addition, the use as an additive to a non-aromatic organic solvent and cosmetics may be impossible. On the contrary, the use of the light polymers may become diverse if halogens are removed therefrom. After the fractional distillation of the light polymers from which halogens are removed, an organic material of C8 to C20 may be used as a non-aromatic organic solvent or an alkylating agent. A heavy organic material with C24 or more is light polybutene having a large molecular weight and a relatively high viscosity and is used as an additive to fuel to act as a friction modifier. In addition, when double bonds in the heavy organic material with C24 or more in the light polymers are removed by a hydrogen addition reaction, a harmless liquid type polymer capable of being used to human may be obtained, and may be used as the additive of cosmetics. According to another method, in order to increase the yield of polybutene having a low molecular weight of about 300 to about 400, an organic material with about C8 is removed, and a polymerization reaction may be performed using light polymers with C12 or more under a solid acid catalyst. By the polymerization reaction, the molecular weight, the viscosity and the polymer portion of the light polymers may increase, and a compound having a molecular weight capable of being used as a fuel additive (friction modifier) and the additive of cosmetics with high value may be obtained.
When polybutene having a low molecular weight of 300 to 400 is prepared in a conventional plant, production cost may increase due to low catalyst yield and low production yield, and profit creation may be difficult. Accordingly, the production and sales thereof may be difficult in consideration of common polybutene. Therefore, the production of polybutene having a low molecular weight by distilling light polymers from which halogens are removed, or the production of polybutene having a low molecular weight by a polymerization reaction under a solid acid catalyst according to the present invention may be greatly effective.
U.S. Pat. No. 6,300,444 discloses a method of removing fluorine by further distilling light polymers including a large amount of fluorine under a reduced pressure to prepare highly reactive polybutene having a low fluorine content. However, according to the method, the fluorine present in the light polymers is not removed, but the light polymers itself is removed via the distillation under a reduced pressure with a high vacuum degree of 2 torr. U.S. Pat. No. 6,476,284 discloses a preparation method of highly reactive polybutene having a vinylidene content of 60% or more and a halogen content of less than 40 ppm, wherein the polybutene is treated using an inorganic solid including an aluminum element. However, with actual application, the amount (mileage) of polybutene treated per unit amount of aluminum inorganic solid is small, and application to a plant is impossible. In addition, the rearrangement of the vinylidene is inevitable. U.S. Pat. No. 6,441,110 discloses a method of preparing highly reactive polybutene using a catalyst of group 3, 4, 5 and 6 without halogens to basically prevent the inclusion of a halogen component, however the catalyst is not commercially available yet. In addition, PCT application No. WO 2005/066220 discloses a method of removing halogens by preparing highly reactive polybutene having a vinylidene content of 50 mol % or more and a molecular weight of 400 to 50,000, removing water to a degree of 10 ppm or less using zeolite, and making contact with the zeolite again. However, since the life of the catalyst is short, the method of removing fluorine using the zeolite could not be used in a commercially used plant, either.
As described above, according to the conventional methods of removing halogens in polybutene and light polymers, the light polymers themselves are removed at a high temperature under a high vacuum degree during preparing polybutene, or the halogen content in a product is decreased or removed via contact with a solid such as an aluminum compound and zeolite. The method of removing the light polymers themselves confronts the present invention, and the method of contacting with the solid such as the aluminum compound and the zeolite is appropriate for batch type removal, however has limitation in continuous removal of halogens when applied to a petrochemical plant. According to this method, silicon (Si) and aluminum (Al) constituting the aluminum compound or the zeolite make contact with an organic halogen at a high temperature and remove halogen from the surface of the solid to form aluminum halogen (AIX) or silicon halogen (SiX), and effects are incomplete.
As described above, in the preparation of polybutene, a large amount of halogens are included in the polybutene thus prepared and in the light polymers produced as a by-product, and the value may decrease and negative affects to human and natural environment may be induced. Accordingly, the use of the polybutene and the light polymers may be limited. Therefore, the removal of halogen from the polybutene and the light polymers is essential to increase the value, to use diversely and not to do harm to human and natural environment.